Help plants dying i think ?

Hello everyone im completly lost for words at the moment this is my second grown !growing 10 x blue cheese in 11lpots
Growing medium coco
Ph 6.2 -6.4
Using dutch pro a /b veg 300 ml each
Dutch pro take root 100 ml
Superthrive 25ml
All mixed in my 100 l barrowl
Temps are 25 / 30 degreese
Growing using 600 w hps

Now to mu problem plants have been in veg for 5 weeks an are all under a foot tall plants look thin an really weak an whole leaves started to og yellow like a pasty green colour geezer in the shop said the were being under nuted an told me to top up on nutes iv got good airfloe with exstract an intake fans aswell as blow fans
Any advice on wtf is happening to my babys an what can i do to stop it asap
A friend said revieve nutrients will stop ot any advise id be very gratful

tbh really need to see a pic of the whole plant to be able to give any real help

From the sounds of it the 'geezer in the shop' was correct.

Nute ppm?

Having trouble uploadin pics from phone onto here any ideas on what the problem might be